string: add __mtag_tag_region

Add optimized __mtag_tag_region(dst, len) operation to AOR. It tags the
given memory region according to the tag of the dst pointer and returns
dst. It requires MTE support. The memory remains untagged if tagging is
not enabled for it. The dst must be 16 bytes aligned and len must be a
multiple of 16.

1 files changed, 147 insertions, 0 deletions

diff --git a/string/test/__mtag_tag_region.c b/string/test/__mtag_tag_region.c
new file mode 100644
index 0000000..d8c02d9
--- /dev/null
+++ b/string/test/__mtag_tag_region.c
@@ -0,0 +1,147 @@
+/*
+ * __mtag_tag_region test.
+ *
+ * Copyright (c) 2021, Arm Limited.
+ * SPDX-License-Identifier: MIT
+ */
+
+#if __ARM_FEATURE_MEMORY_TAGGING && WANT_MTE_TEST
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include "mte.h"
+#include "stringlib.h"
+#include "stringtest.h"
+
+static void
+mtag_quoteat (const char *prefix, void *p, int len, int at)
+{
+  /* Print tag, untag and quote the context.  */
+  printf ("location: %p\n", __arm_mte_get_tag ((char *) p + at));
+  untag_buffer (p, len, 1);
+  p = untag_pointer (p);
+  quoteat (prefix, p, len, at);
+}
+
+#define F(x) {#x, x},
+
+static const struct fun
+{
+  const char *name;
+  void *(*fun) (void *s, size_t n);
+} funtab[] = {
+// clang-format off
+#if __aarch64__
+  F(__mtag_tag_region)
+#endif
+  {0, 0}
+  // clang-format on
+};
+#undef F
+
+#define A 64
+#define LEN 250000
+static unsigned char *sbuf;
+
+static void *
+alignup (void *p)
+{
+  return (void *) (((uintptr_t) p + A - 1) & -A);
+}
+
+static void
+test (const struct fun *fun, int salign, int len)
+{
+  unsigned char *src = alignup (sbuf);
+  unsigned char *s = src + salign;
+  void *p;
+  int i;
+
+  if (err_count >= ERR_LIMIT)
+    return;
+  if (len > LEN || salign >= A)
+    abort ();
+  for (i = 0; i < len + 2 * A; i++)
+    src[i] = '?';
+  for (i = 0; i < len; i++)
+    s[i] = 'a';
+
+  src = tag_buffer (src, len + 2 * A, 1);
+  s = src + salign;
+  /* Use different tag.  */
+  s = __arm_mte_increment_tag (s, 1);
+  p = fun->fun (s, len);
+
+  if (p != s)
+    ERR ("%s(%p,..) returned %p\n", fun->name, s, p);
+
+  for (i = 0; i < salign; i++)
+    {
+      if (src[i] != '?')
+	{
+	  ERR ("%s(align %d, %d) failed\n", fun->name, salign, len);
+	  mtag_quoteat ("got head", src, len + 2 * A, i);
+	  return;
+	}
+    }
+
+  for (; i < salign + len; i++)
+    {
+      if (s[i - salign] != 'a')
+	{
+	  ERR ("%s(align %d, %d) failed\n", fun->name, salign, len);
+	  mtag_quoteat ("got body", src, len + 2 * A, i);
+	  return;
+	}
+    }
+
+  for (; i < len + 2 * A; i++)
+    {
+      if (src[i] != '?')
+	{
+	  ERR ("%s(align %d, %d) failed\n", fun->name, salign, len);
+	  mtag_quoteat ("got tail", src, len + 2 * A, i);
+	  return;
+	}
+    }
+
+  untag_buffer (src, len + 2 * A, 1);
+}
+
+int
+main ()
+{
+  if (!mte_enabled ())
+    return 0;
+
+  sbuf = mte_mmap (LEN + 3 * A);
+  int r = 0;
+  for (int i = 0; funtab[i].name; i++)
+    {
+      err_count = 0;
+      for (int s = 0; s < A; s += 16)
+	{
+	  int n;
+	  for (n = 0; n < 200; n += 16)
+	    {
+	      test (funtab + i, s, n);
+	    }
+	  for (; n < LEN; n *= 2)
+	    {
+	      test (funtab + i, s, n);
+	    }
+	}
+      printf ("%s %s\n", err_count ? "FAIL" : "PASS", funtab[i].name);
+      if (err_count)
+	r = -1;
+    }
+  return r;
+}
+#else
+int
+main ()
+{
+  return 0;
+}
+#endif